Landfill reclamation

ABSTRACT

A method of increasing the capacity of an existing landfill to enable the disposal of additional material therein includes excavating material disposed in the existing landfill, separating from the excavated material one or more components thereof, comminuting the components of the excavated material which are not removed by the previous step, and placing the comminuted material back into the landfill.

CROSS-REFERENCE TO RELATED APPLICATION

This is a continuation-in-part of U.S. patent application Ser. No.08/169,679 which was filed on Dec. 17, 1993.

FIELD OF THE INVENTION

This invention relates to methods and apparatus for increasing thecapacity of an existing landfill site thereby allowing additionalmaterial to be disposed therein.

BACKGROUND OF THE INVENTION

Environmentally sound landfill space is becoming increasingly scarcethroughout the United States, particularly in the more densely populatedurban and coastal areas. Older landfills are closing at a rate farexceeding the opening of replacements. Landfills are closing because ofa variety of reasons including threat to the environment, refusal of thesurrounding community to accept the continued operation of the landfillas is, and full utilization of available space.

It is becoming increasingly difficult to site new landfills because, forexample, of environmental regulations that do not allow landfills to belocated on "marginal" land (e.g., land generally not suitable ordesirable for commercial or residential purposes) which is where many ofthe older landfills are located. As older landfills close, new landfillsmust compete for non-marginal land which can be put to other, and somethink better, uses. Evidence of this competition can be seen from therelatively few sitings of new "greenfield" landfills in the morepopulated areas of the U.S.

Incinerators were once thought to be a solution to the problemspresented by landfills, but incinerators have met with such publicopposition that they are not likely to be the total solution. Also,incinerators and other known mainstream waste management technologiestypically require landfill space as a component in their overallapproach to waste management. For example, recycling and incinerationcan each reduce the volume of waste, but landfill space is stillrequired for the disposal of non-recyclables and ash. Thus, while thevolume of waste which must be disposed of in a landfill can be decreasedby these and other known waste management programs, it generally is notpossible to eliminate the need for landfill space. Those knowledgeablein the field of waste management agree that landfill space will beincreasingly valuable in the next decade and beyond.

One waste management program which has been relatively successful (e.g.,it accounts for most of the new landfill capacity in urban areas of theU.S.) is the expansion of the size (area) of some existing landfills.The existing landfills which have been expanded in size generally arewell sited to begin with and also have community support for continuedoperation.

SUMMARY OF THE INVENTION

The present invention is directed to increasing the capacity of existinglandfills, not necessarily by expanding the size of the landfills, butinstead by reclaiming or remodeling the existing landfill space. Inaccordance with the invention, material is excavated from an existinglandfill, and the excavated material is processed to reduce its volumethereby allowing its close packed disposal back into the existinglandfill from which it was excavated.

The processing of the excavated material can involve a variety ofoperations such as screening, comminution (e.g., shredding), and/ormechanical compaction. The various processing operations can beperformed in a variety of combinations. For example, the excavatedmaterial can be screened to reduce its volume, shredded to furtherreduce its volume, and then screened again to even further reduce itsvolume. The screening steps can be performed by a screening orseparating device such as a trommel.

With the invention, it is possible to increase the capacity of anexisting landfill by between about 20 to about 80%; that is, betweenabout 20 to about 80% of the previously used volume of the existinglandfill can be recovered. Results can vary depending on, for example,how well material in the existing landfill was compacted and the typeand amount of cover used. Recoveries of between about 50 to about 80%,between about 65 to about 80%, and between about 70 to about 80% alsoare possible with the invention.

Recyclables and other valuable components of the excavated material canbe separated from the excavated material before it is placed back intothe existing landfill, thus further reducing the volume of the excavatedmaterial. For example, ferrous metals can be separated from theexcavated material. In general, only components that are present insufficient quantity such that they can be cost effectively recovered andsold will be separated from the excavated material.

The excavated material typically includes soil and refuse. The soil canbe separated from the refuse and stored for later use (e.g., as cover inthe landfill) or sold as clean fill, thus further reducing the volume ofthe excavated material. In general, more soil will be recovered from theinventive process than will be needed as cover. The extra separated soilcan be cleaned further, if needed, and then sold as clean fill.

In accordance with the present invention, one or more of the steps ofexcavating material from the existing landfill, processing it to reduceits volume, and then returning the excavated, processed material to theexisting landfill can be conducted under a temporary enclosure built tocover the existing landfill. The temporary enclosure is useful in, forexample, preventing odors from being released into the surroundingenvironment (or at least reduce the amount thereof), and suppressingnoise, if required.

As part of increasing the capacity of the existing landfill, theinvention can include the step of preparing a disposal cell at a sitewithin the landfill in conformance with prevailing environmentalregulations. The excavated and processed material then can be placedwithin the environmentally safe cell. The cell can be located at thearea from which the material was excavated, or it can be located inanother area of the existing landfill. The amount of work needed tobring the cell up to current regulatory standards will vary by landfill.Current environmental regulations typically require safeguards such asliners and leachate treatment facilities.

The invention can be used to increase the capacity of existing landfillswhich are already permitted under the applicable (environmental)regulations.

Other objects, aspects, features, and advantages of the invention willbecome apparent from the following description and from the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is flowchart of a process for increasing the capacity ofexisting landfills in accordance with the invention.

FIG. 1B is a block diagram of an existing landfill.

FIG. 2 is a flowchart of another process for increasing the capacity ofexisting landfills in accordance with the invention.

FIG. 3 is a flowchart showing more detail of a step performed as part ofthe processes of FIGS. 1 and 2.

FIG. 4 is a diagram of a particular landfill reclamation processaccording to the invention.

FIG. 5 is a perspective view of cutters of a shredding machine for usein processes according to the invention.

DESCRIPTION

A method for increasing the capacity of an existing, permitted landfillaccording to the invention typically is performed in stages. That is,the landfill typically is divided into one or more separate areas, andthe present method is employed consecutively at each of the areas untilall space in the landfill is reclaimed according to the invention. As analternative to reclaiming space in the landfill piecemeal, it ispossible to reclaim all space in the landfill by one operation.

Referring to FIGS. 1A and 1B, a method according to the invention forreclaiming space in an existing, permitted landfill 100 and thusincreasing the capacity of that landfill 100 typically involves, as aninitial step 10, constructing a storage area 102 within the landfill100. The storage area 102 is constructed to meet all applicableregulatory standards (e.g., environmental regulations) such that, uponcompletion, it will provide environmentally safe storage space formaterial removed from another area of the landfill 100 and processedaccording to the invention. The storage area 102 can includeenvironmental control structures such as leachate collection.

With the storage area 102 created (step 10), a given volume of materialcan be excavated (step 12) from a worksite 104 within the landfill 100(i.e., an area other than the storage area 102) and processed (step 14)to reduce its volume thereby allowing the excavated, processedmaterial's close packed disposal or storage in a volume less than thegiven volume. The material typically includes refuse and soil. Anhydraulic track backhoe, or similar piece of excavation equipment, canbe used to excavate the material from the worksite 104. The processingstep 14 can include comminuting the material (e.g., with a shredder orother comminution equipment) to reduce its particle size. As describedbelow with reference to FIGS. 3, 4, and 5, the processing step 14 caninclude a variety of other steps in addition to, or besides,comminution. After the excavated material is processed (step 14), it isstored (step 16) on-site in the storage area 102.

In general, the steps of excavating (step 12), processing (step 14), andstoring (step 16) are repeated, as indicated by a feedback arrow 18,until substantially all material in the worksite 104 is excavated,processed, and stored. These three steps can be repeated on anaround-the-clock basis until the worksite 104 is substantially empty, orthey can be repeated only during a working day. Because of the dailyinterruption, the latter approach typically requires more time to emptythe worksite 104 of material than the former approach. Aftersubstantially all material from the worksite 104 is excavated,processed, and stored in the storage area 102, the worksite 104 isreconstructed to bring it up to current regulations (step 20).

The reconstruction effort (step 20) may include the installation of newliners, leachate control systems, and/or methane recovery systems. Ingeneral, any measures necessary under the current environmentalregulations are taken. The technology and construction techniquesrequired to conform the excavated worksite to the applicable regulationsare known to those of ordinary skill in the art.

In one embodiment of the present reclamation method, equipment is thenmoved to a new worksite 106 (step 22), and the excavation, processing,and storing steps are repeated, as indicated by a feedback arrow 24. Thematerial that is excavated (step 12) from the new worksite 106 isprocessed (step 14) as before and then placed in the previous worksite104 (step 16) which acts now as the storage area for the processedmaterial excavated from the new worksite 106. The sequence of stepsfalling within the feedback arrow 24 are repeated until all areas of thelandfill 100 requiring attention are treated according to the invention.

In another embodiment of the present reclamation method, after step 20,the processed material in the storage area 102 is returned to theworksite 104 (step 26), and the equipment is then moved to a newworksite 106 (step 28) where the excavation, processing, and storingsteps are repeated, as indicated by a feedback arrow 30. The materialthat is excavated (step 12) from the new worksite 106 is processed (step14) as before and then placed in the storage area 102 (step 16). Thesequence of steps falling within the feedback arrow 30 are repeateduntil all areas of the landfill 100 requiring attention are treatedaccording to the invention. The storage area 102 is thus usedexclusively in this embodiment as a temporary on-site storage location.

Regardless which of the two previously described embodiments (orcombinations thereof) are employed, the present method results in thereclamation of space in the landfill 100 such that the capacity of thelandfill 100 is increased. Because of this increase in capacity,additional refuse can be disposed therein. The present method alsoresults in an environmentally safer landfill because all currentregulations will be met by the landfill after installation. Thus,landfills remodeled by the present method can continue to operatewithout threat to the environment.

In general, the entire landfill is not shut down when treatmentaccording to the invention begins. Some sections of the landfill 100typically will continue to operate (i.e., receive refuse for disposaltherein) while other sections of the landfill 100 are treated accordingto the invention. This approach has the advantage that revenue from theoperating portion of the landfill can be used to pay for or offset thecost of treating the other portions of the landfill. Also, after thefirst worksite is excavated and brought up to current regulations, thatworksite can begin to operate as an environmentally safe disposal cellby accepting refuse from outside sources even if the rest of thelandfill has yet to be treated according to the invention.

In another embodiment of the invention, the repetitive process (arrow 24and/or arrow 30) described previously with reference to FIG. 1A ispreceded by a series of steps which, in general, are necessary when thelandfill being treated cannot store on-site the processed materialexcavated from an initial worksite. Reasons why this processed materialcannot be stored on-site can vary. One reason might be that the landfillis full to capacity. In general, the decision whether to create anon-site storage area for the processed material excavated from theinitial worksite (FIG. 1A) or to ship this processed material off-sitefor disposal (FIG. 2) is made by considering the current status of thelandfill and the cost of off-site disposal.

Referring to FIG. 2, when the decision is made to ship off-site theprocessed material excavated from the initial worksite in the landfill,the series of steps which precede the repetitive process (arrow 24and/or arrow 30) described previously with reference to FIG. 1A includethe following. The material that is excavated from the initial worksite(step 32) is processed (step 34) as described previously, and theprocessed material is shipped off-site for disposal (step 36). Asindicated by a feedback arrow 38, these excavating, processing, andoff-site shipping steps are repeated until substantially all material isexcavated from the initial worksite. Thereafter, the initial worksite isreconstructed to bring it up to current regulations (step 40). (Thisreconstruction is performed as described previously for step 20 in FIG.1A). The excavation and processing equipment is then moved to a newworksite (step 42) within the landfill, and treatment continues in therepetitive loop (arrow 24 and/or arrow 30) previously described. Thenow-environmentally-safe initial worksite acts as the on-site storagearea in (at least) the first loop of the repetitive loop. In effect, thepreceding steps 32, 34, 36, 40, and 42 serve to create anenvironmentally-safe, on-site storage area when it is physically and/oreconomically not viable to do so as the initial step in the presentreclamation method.

Referring to FIG. 3, the processing step (step 14 and step 34) used inthe methods of FIGS. 1A and 2 can include a variety of sub-steps such ascomminution (sub-step 44), separation (sub-steps 46 and 48), andcompaction (sub-step 50). While these processing sub-steps are shown ina particular order, it is possible and frequently advantageous toperform one or more of these sub-steps in an order different than thatshown in FIG. 3. It also is possible to repeat and/or eliminate certainsteps. In general, a variety of combinations of processing sub-steps arepossible.

In one embodiment according to the invention, the processing isperformed by separating certain components from the excavated material(e.g., by screening soil from the excavated material with a screeningand/or separating device such as a trommel), comminuting (e.g.,shredding) the excavated material remaining after the certain componentshave been separated therefrom, and then separating components (e.g.,screening out more soil) from this comminuted material. Thus, in thisembodiment, the given volume of excavated material is reduced byprocessing sub-steps which can include screening, shredding, and thenscreening a second time. In another embodiment, the processing sub-stepsare as shown and described below with reference to FIG. 4.

In general, the comminution sub-step 44 is performed to reduce theparticle size of the excavated material. The comminution sub-step 44preferably is performed by shredding, and more preferably is performedby a low speed shear shredder machine described below with reference toFIGS. 4 and 5.

Separation sub-steps can be performed on the excavated material.Separation operations can include the removal of soil from the excavatedmaterial (sub-step 46) and/or the removal of other valuable componentsfrom the excavated material (sub-step 48).

The removal of soil will reduce the volume of the excavated material.The soil can be separated out by, for example, screening the excavatedmaterial and/or by using a trommel system as described below withreference to FIG. 4. Other screening or separating devices can be usedinstead of the trommel system. The separated soil can be stored forlater use (e.g., as cover in the landfill). In general, more soil willbe recovered from the inventive reclamation method than will be neededas cover. The extra separated soil can be cleaned further, if needed,and then sold as clean fill.

The removal of other valuable components (sub-step 48) will reduce thevolume of the excavated material. A variety of valuable components canbe separated from the excavated material. For example, ferrous materials(e.g., metals) can be separated out, collected, and sold. Such metalscan be separated out, for example, by use of a magnet. Other separationtechniques are possible to remove such metals. Other components whichcan be separated from the excavated, comminuted material include paper,plastic, wood, aluminum, glass, and similar materials.

In general, in each of the processing sub-steps 46 and 48, thecomponents removed from the excavated material (e.g., soil and ferrousmaterials) are components which are valuable and which can be recoveredin such a large quantity that they can be collected and sold for aprofit. Revenue received from the sale of these valuable components canbe used to pay for or offset the cost of reclaiming the landfill inaccordance with the invention. While the removal of soil and ferrousmaterials from the excavated material is described in most detailherein, other components also can be removed if those other componentsare (i) valuable and (ii) recoverable in a large enough quantity thatthey can be sold for a profit.

Compaction (sub-step 50) can be performed to reduce the volume of theexcavated material. The compaction can be performed by a mechanicalcompactor such as that described below with reference to FIG. 4.

As stated previously, the processing sub-steps have been presented in aparticular order, but it is possible to perform one or more of them inan order different than that shown in FIG. 3, and it is possible torepeat and/or eliminate particular sub-steps. For example, theprocessing of the excavated material can include shredding, mechanicalcompaction, soil removal, ferrous material removal, and then a secondcompaction operation. As another example, the processing can include afirst separation step, shredding, and then a second separation step. Ingeneral, each of the processing sub-steps reduces the volume of thematerial on which that sub-step operates.

In some embodiments of the landfill reclamation method according to theinvention, the processing (steps 14 and 34 of FIGS. 1A, 2, and 3) of theexcavated material is conducted under a temporary enclosure set upwithin the landfill. The excavating step (steps 12 and 32 of FIGS. 1Aand 1B) and/or storing step (step 16 in FIG. 1A) also can be conductedunder a temporary enclosure. One or more temporary enclosures can beused to cover the areas where such operations are conducted. Temporaryenclosures are useful in, for example, preventing comminuted materialand/or odors from being released into the surrounding environment (or atleast reduce the amount thereof), and suppressing noise created by theexcavating, processing, and/or storing operations. The temporaryenclosures can be constructed before, during, or after the constructionof the initial storage area 102 of FIG. 1B (step 10, FIG. 1A). In theembodiment of FIG. 2, the temporary enclosures can be constructed beforethe excavation (step 32) begins. The temporary enclosures can betent-like structures of, for example, a cloth or plastic material.

Referring to FIG. 4, an embodiment of a landfill reclamation processaccording to the invention involves constructing, in an existing,permitted landfill 52, a storage area 54 which complies with allapplicable regulatory standards (e.g., environmental regulations). Thestorage area 54 is an environmentally-safe storage space for materialexcavated from an excavation area 56. In the disclosed embodiment, thestorage area 54 includes a state-of-the-art liner and leachatecollection system. In other embodiments, the storage area 54 can includesimply plastic over the ground with an appropriate leachate collectionsystem, if needed.

An hydraulic track backhoe 58 is used to excavate material from theexcavation area 56. The backhoe 58 deposits the excavated material intoa low speed shear shredder 60 which has a screen at its outlet throughwhich dirt 62 can pass. As indicated by an arrow 64, the dirt 62 iscollected in a mound 66 for use, for example, as cover material in thestorage area 54. In the disclosed embodiment, the shredder 60 can shredup to about 100 tons of material per hour, and it has a 200 horsepowerengine for driving the cutting/shredding mechanism of the shredder 60.Suitable low speed shear shredders are available commercially from ShredPax Corp. of Wood Dale, Ill. Models AZ-160 and AZ-200 from Shred Pax areparticularly suited for use as shredders in the present landfillreclamation process. Depending on the model of Shred Pax shredder, theShred Pax shredder can handle up to about 300 tons of material per hourand have motors ranging from 7 to 300 horsepower. As shown in FIG. 5,these Shred Pax shredders have counter-rotating cutters 68 and 70 whichare very effective at comminuting and shredding a variety of wastematerials.

In some embodiments, the backhoe 58 deposits the excavated material intoa separating or screening device 59 such as a trommel, screen, orshaking device. A suitable device is commercially available from TheRead Corporation, 25 Wareham Street, Middleboro, Mass. 02346 as the ReadWaste Manager model W/M 3500 or W/M 3000. The separating device 59 isshown as a block for simplicity. In these embodiments, the excavatedmaterial is pre-separated or pre-screened before it reaches the shredder60. A variety of components can be pre-separated or pre-screened fromthe excavated material by the device 59. The device 59 can remove dirt62 from the excavated material, which dirt 62 can then be collected inmound 66.

Note that, as indicated in FIG. 4, various items in the excavation area56 can be removed from the refuse before excavation by the backhoe 58 orbefore comminution by the shredder 60 (or before separation by thedevice 59 if such a device is employed). Those items can include rockand rubble 72 and "white goods" (e.g., household appliances such asrefrigerators, stoves, washers, dryers, and dishwashers) and tires 74.The white goods and tires 74 are representative of recyclables ingeneral. The rock and rubble 72 are representative of fill materialswhich can be placed directly into the storage area 54 without beingprocessed.

Still referring to FIG. 4, the shredder 60 can be followed by acompaction/transportation device 76 which mechanically compacts materialand then transports it to a trommel system 78 (or other separating orscreening device). A suitable compaction/transportation device isavailable commercially as Model AZ PAX from Shred Pax Corp. of WoodDale, Ill. This Shred Pax device has a motor with from 50 to 75horsepower.

Instead of following the shredder 60 with the compaction/transportationdevice 76, the shredder 60 can feed a metal-belt or rubber-belt conveyorsystem (i.e., a conveyor system which does not also compact the materialbeing conveyed as does the compaction/transportation device 76). Acompactor/transporter can be preferred over just a transporter becausethe compactor/transporter (e.g., the device 76) generally eliminatesmaintenance and belt-wear problems associated with conveyor systemshaving metal or rubber conveyor belts.

Regardless of whether a combined compaction/transportation device or atransporting system alone is utilized in moving material from theshredder 60 to the trommel system 78, the trommel system 78 (or otherseparating or screening device) receives the material and removes dirttherefrom. This dirt is then collected. In the disclosed embodiment, itis collected at the mound 66 for later use as cover material in thestorage area 54. In general, a trommel is a type of a screen in that itperforms a screening operation in which an incoming stream is separatedinto two or more fractions based on size. The trommel is a sloped,rotating (as indicated by arrows 82), screen-covered drum. The screencovering can be either a wire mesh or a punched plate, the later type ofscreen covering being more typical. The slope and rotation of thetrommel causes the input material to advance therethrough. The rotationensures that all of the input material to the trommel is presented tothe screen covering. Advantages of the trommel over other screeningsystems (e.g., a vibrating screen, a disk screen, or a power screen)include the trommel's ability to thoroughly mix and tumble the feedstream.

The material exiting the trommel system 78 is transferred to a magneticseparator 80 which removes ferrous material 82 therefrom. The ferrousmaterial is collected. In transferring the material exiting the trommelsystem 78 to the magnetic separator 80, a simple conveyor system isused. The reduced-volume output of the magnetic separator (i.e., theshredded, compacted, and substantially rock-, rubble-, recyclables-,soil-, and ferrous material-free material) is then compacted (e.g., by acompactor available commercially from Shred Pax Corp. of Wood Dale,Ill.) to reduce even further its volume. The resulting material is thenplaced in the storage area 54.

The landfill reclamation process of FIG. 4 produces clean dirt 66 andferrous materials 82 which each can be sold for a profit, and it resultsin a recovery of between about 20 to about 80% of the volume of the oldlandfill. In the embodiment of FIG. 4 and some other embodimentsaccording to the invention, the process can result in a recovery ofbetween about 50 to about 80%, and more preferably between about 65 toabout 80%, and most preferably between about 70 to about 80%.

Other modifications and implementations will occur to those skilled inthe art without departing from the spirit and the scope of the inventionas claimed. Accordingly, the invention is to be defined not by thepreceding illustrative description, but by the following claims.

What is claimed is:
 1. A method of increasing the capacity of anexisting landfill to enable the disposal of additional material therein,comprising:(A) excavating from the existing landfill material includingone or more components; (B) separating one or more of the componentsfrom the excavated material; (C) comminuting the components of theexcavated material which are not removed by step (B); and (D) placingthe comminuted material back into the landfill.
 2. The method of claim 1further comprising preparing a disposal cell at a site within thelandfill in conformance with prevailing environmental regulations. 3.The method of claim 2 wherein step (D) comprises placing the comminutedmaterial into the disposal cell.
 4. The method of claim 2 wherein thepreparing step comprises preparing the disposal cell at an area of thelandfill from where the material is excavated in step (A).
 5. The methodof claim 2 wherein the preparing step comprises preparing the disposalcell at an area of the landfill different from where the material isexcavated in step (A).
 6. The method of claim 1 further comprisingseparating ferrous metals from the excavated material prior to step (D).7. The method of claim 1 further comprising separating soil from theexcavated material prior to step (D).
 8. The method of claim 7 furthercomprising compacting the excavated material prior to step (D).
 9. Themethod of claim 1 further comprising compacting the excavated materialprior to step (D).
 10. The method of claim 1 wherein step (C) comprisesshredding.
 11. The method of claim 1 wherein step (C) is conducted undera temporary enclosure.
 12. A method of increasing the capacity of anexisting, permitted landfill to enable the disposal of additionalmaterial therein, comprising:(A) preparing a disposal cell at a sitewithin the existing, permitted landfill in conformance with prevailingenvironmental regulations; (B) excavating from the landfill materialhaving one or more components; (C) separating one or more componentsfrom the excavated material; (D) shredding the components of theexcavated material which are not removed by step (C); (E) separatingsoil from the shredded material; (F) separating ferrous metals from theshredded material; and (G) placing within the disposal cell theexcavated, shredded material from which the one or more components, thesoil, and the ferrous metals have been separated.
 13. The method ofclaim 12 further comprising using at least a portion of the soil whichis separated from the excavated, shredded material as cover in thedisposal cell.
 14. The method of claim 12 wherein step (F) is conductedby placing a magnet over the shredded material.
 15. The method of claim12 further comprising separating at least one valuable component fromthe excavated, shredded material prior to step (G).
 16. The method ofclaim 15 wherein the valuable component comprises paper.
 17. The methodof claim 15 wherein the valuable component comprises plastic.
 18. Themethod of claim 15 wherein the valuable component comprises Wood. 19.The method of claim 15 wherein the valuable component comprisesaluminum.
 20. The method of claim 15 wherein the valuable componentcomprises glass.
 21. The method of claim 12 further comprisingcompacting the excavated material prior to step (G).